Pectic enzymes of nonphytopathogenic Klebsiella and Yersinia strains have been-isolated, purified, characterized, and compared with those from the phytopathogen Erwinia chrysanthemi. The major pigment of Pseudomonas paucimobilis, a nosocomial human pathogen previously confused with Xanthomonas (Weaver's group IIK, biotype 1), is a carotenoid (nostoxanthin) and not a brominated aryl-polyene (xanthomonadin) pigment of the sort invariably formed by xanthomonads. Xanthomonadin pigments protect Xanthomonas against photodynamic damage (probably in the same way as carotenoids do). A dialyzable, ethanolsoluble fraction was isolated from associations between virulent Reqinia amylovora strains and pear cell cultures; this material (a putative necrotoxin) shows strong necrotoxic activity against pear cell cultures and pear seedlings. Electron microscopy of thin-sections provides no ultrastructural basis for the known "leakiness" of virulent strains of Erwinia amylovora; we are turning to freeze-fracture and -etching techniques. The E-lac plasmid from a clinical strain of Erwinia herbicola has been fully characterized. Plasmids have been isolated from erwinia amylovora and Corynebacterium fascians; they are being characterized, including their possible roles in plant virulence. We have indirect evidence that members of the Blastocaulis-Planctomyces group of budding and appendaged bacteria inhabit plants; a direct search is being made for them on vegetation. Serratia strains have been isolated from plants and are being biotyped; they will be compared with Serratia strains isolated from human nosocomial infections.